The present invention relates generally to storage systems and, more particularly, to the management of special rearrangement in automated page-based tier management regarding storage resources.
Hierarchical storage management also called tier management is a storage management method designed for improving the utilization of storage resources in computer systems. Specifically, the utilization of resources is optimized by changing the location of data among storage resources in a computer system based on the worth and usage of the data in the enterprise. On the other hand, the analysis and the classification of the aforesaid worth and the usage are generally complicated tasks. Therefore, recently some storage system vendors proposed automated page-based tier management performed by a storage system. With this function, the storage system monitors access characteristics of each small data storage area, such as a page, in a data storage volume, or a file system region, and automatically relocates the data in the page based on the detected access characteristics. See, e.g., U.S. Patent Publication No. US2010/0077168. In addition, U.S. patent application Ser. No. 12/560,740, filed Sep. 16, 2009, discloses methods and apparatus for dynamic page reallocation storage system management. That invention provides a technique whereby the storage indicates the current tier load, the storage user can change the tier configuration rule, and the storage can reconfigure the tier configuration according to the tier configuration rule set by the storage user. In this way, the storage system can dynamically change the tier configuration based on input from the storage user according to the actual tier load. The entire disclosures of these references are incorporated herein by reference.
Using pages mentioned above for providing data storage volumes can achieve reduction of storage cost, management cost, and power consumption. This approach is called thin provisioning for storage. With thin provisioning, a storage system provides virtual volumes as storage area to store data for computers. For the virtual volumes, the storage system allocates and assigns physical area to only locations having write access of the computers. The total amount of used physical area in the pool can be smaller than the total amount of virtual area shown to the computers. To realize this capability, the storage system divides the storage area (e.g., storage area in HDD or flash memory) to a plurality of fixed-length areas called chunks or pages, and manages mapping between chunks and logical segments in the virtual volumes.
In addition to the aforesaid automated control, users need to make special rearrangement of data location for specific volumes, for example, to solve unexpected performance problems regarding use of data stored in the volumes. The manual rearrangement of data in tiered storage is also useful when the users can predict usage of data or have plan to use the data, in order to realize more efficient use of storage resources.